1. Field of the Invention
The present invention relates to signal detecting systems and, more particularly, to a signal detecting system using telephone lines for signal transmission.
2. Description of Related Art
In recent years, hidden or pinhole cameras have been used for immoral spying on private affairs in houses or certain locations such as hotels. The behavior immoral spying with hidden or pinhole cameras is a serious offence against public interests, particularly privacy and intimacy.
To solve the problems of immoral spying with hidden or pinhole cameras, a “System and Method for Preventing to Use Portable Terminal Having Camera As Secret Spy Camera,” as disclosed in U.S. Publication No. 2005/0075117 A1, uses a Radio Frequency Identification (RFID) module to pause the camera function of a portable terminal, such that the camera function can be automatically limited at a specific place to prevent illegal photographing. Nevertheless, radio frequency through wireless transmission can be easily disrupted by terrain or topography, and as such, the effectiveness of camera function pausing is greatly reduced. Besides, in receiving, transmitting or identifying signals, it is necessary to employ a specific device, accompanied with an RFID technique but this increases the cost of system construction and the complexity of design.